Rubbery polymers plasticized with thio derivatives of polychlorobenzenes



United States Pater Q RUBBERY POLYMERS PLASTICIZED WITH THIO DERIVATIVES F POLYCHLOROBENZENES Friedrich Lober, Otto Bayer, and Max Btigemann, Leverkusen-Bayerwerk, and Paul Schneider, Opladen, Germany No Drawing. Original application December 27, 1950, SerialNo. 207,068, now Patent No. 2,695,898, dated November 30, 1954. Divided and this application May 20, 1954, Serial No. 431,283

l Claims priority, application Germany December 27, 1949 3 Claims. (Cl. 26030.8)

The present invention relates to the plasticizing of rubher and rubber-like polymerizates and further relates to the reclaiming of their vulcanizates.

It is known that aromatic mercaptans, such as thiophenol or alkyland/or trihalogen substitution products thereof and thionaphthols as well as their zinc salts promote the mastication of natural rubber and synthetic rubber-like butadiene-polymers at elevated temperatures. However, these compounds possess a very unpleasant odor which is characteristic for mercaptans and, due to their more or less great volatility at the mastication temperatures usually employed, especially when simultaneously subjecting the rubber to mechanical treatment in the generally used aggregates, cause strong annoyances of the olfactory nerves and in most cases a dermatitis.

It has been found that penta-substituted thiophenols carrying at least 4 Cl-atoms in the nucleus, such as pentachloroand tetrachloro-alkylthiophenols or the functional derivatives thereof, are excellent agents for plasticizing high polymeric plastics, such as unvulcanized natural rubber or synthetic rubber-like polymerizates, and for reclaiming vulcanizates thereof. The sai-d'penta-substituted thiophenols are superior to the known aromatic mercaptans since they show an excellent plasticizing effect by which they are distinguished despite their molecular enlargement and cause only a very weak annoyance of the olfactory nerves because they are only slightly volatile. The penta-substituted thiophenols carrying at least 4 Clatoms in the nucleus are further distinguished by their sulfhydryl group giving a considerably weaker reaction than the thiophenols usually employed. When synthetic rubber-like butadiene polymers are plasticized with thiophenols by subjecting the polymers to a thermal treatment for a longer period than is necessary for accomplishing the desired plasticity cyclization of the polymerizates cannot be avoided. However, on using the penta-substituted thiophenols cyclization is brought about only to an immaterial degree and when the S-acyl derivatives of said penta-substituted thiophenols are employed, cyclization does not occur at all. The penta-substituted thiophenols iri the technically pure state already represent odorless compounds which give the known mercaptan reactions and are readily soluble in aromatic hydrocarbons. The functional derivatives of the said thiophenols which are capable of reforming the penta-substituted thiophenols by reduction, hydrolysis, or by disproportioning in the mastication are equally suited.

Another advantage of the new penta-substituted thiophenol plasticizers resides in the fact that they are effective at essentially lower temperatures than those applied when operating with the usual plasticizing agents. In some cases, a suificient plasticizing effect is achieved simply at 80 to 95 C. Furthermore, the new plasticizing agents show the special advantage that the plasticizing starts almost immediately after beginning the, treatment and after a short period a satisfactory plasticity is r 2,775,568 Patented Dec. 25, 1956 achieved. Therefore, when utilizing the plasticizers according to the present invention, plasticizing is achieved within a, substantially short period. Furthermore, the new plasticizing agents which are almost odorless do not cause any health hazards e. g. skin diseases of the attendants handling therewith and are not toxic. Therefore, they are adapted for producing rubber articles intended for use in contact with foodstuffs. The fillers, antioxidants and accelerators with exception of the thiuram compounds, generally employed in the rubber industry as well as the other usual auxiliary agents do not affect the plasticizing procedure performed with the new penta substituted thiophenol compounds.

The new plasticizing agents correspond to the general formula:

In this formula and in the following formulae R stands for CsClsor C6Cl4'alk.-, alk. representing an alkyl group with 1 to 8 C-atoms or more. X stands for a member of the group consisting of -SO2-aliphatic and -SO2-aromatic.

According to the present invention the following pentasubstituted thiophenols or functional derivatives thereof are useful: penta-chloro-thiophenol, the zinc salt of pentachloro-thiophenol, pentachloro-thiophenyl acetic ester, pentachloro-thiophenyl propionic ester, the ester of pentachloro-thiophenol with the fatty acids of the first runchlorophenyl-mercaptal, furfurylaldehyde-bis-pentachlorophenyl-mercaptal, S-pentachlorophenyl thioacetonitrile, N-phenyl-S-pentachlorophenyl-thiourethane, hexamethylene di (S-pentachloro-phenylthiourethane), di-S-pentachlorophenyl-dithio-carbonic ester, and the corresponding functional derivatives of the methyl-tetrachloro-thiophenol, ethyl-tetrachloro-thiophenol, butyl-tetrachloro-thiophenol, cyclohexyl-tetrachloro-thiophenol and isooctyltetrachloro-thiophenol. Pentachloro-thiophenol, the zinc salt of pentachloro-thiophenol, di-pentachlorophenyl-disulfide, benzoyl-pentachloroand acetyl-pentachloro-thiophenol have proved to be especially useful in practice.

The increased plasticizing effect of the said penta-substituted thiophenols over the hitherto used aromatic mercaptans, for instance, the trichloro-thiophenol, is achieved by the substitution of the hydrogen atoms in the aromatic nucleus by chlorine or by chlorine and one alkyl, the substituents exerting an activation effect upon the mercapto group. The disulfides of the thiophenol, thionaphthol and the low chlorinated aromatic mercaptans, e. g. trichlorothiophenols, accelerate the rate of plasticizing only to an immaterial degree. The sulfur bridge of the dipentasubstituted diphenyl-disulfides with at least 4 Cl-atoms in 3 tion of the'aromatic nucleus, to such an extent that they showin" the plasticizin'g procedure ana'cti'vity which is only slightly inferior to that of the pentachloro-thiophenol.

The new compounds according to the present inven tion arepreferablyemployed in-quantities of0.l to;5 fbnpla'stieizing unvulcani zed natural rubber and' in quantities ofOIZSto 3% fo'r plasticizin'gsyntheticrubberlike butadiene'polymersiandare' equally suitedfor reclaiming vulcanized natural rubber, and vulcanized rubher-like butadiene polymers.

The term synthetic rubber-like butadi'ene polymers shall comprise the polymerizates' of butadiene or its homolo'gues; such=as isoprenea'nd dirn'ethyl-butadiene as wellas=-copolymerizates' of said' co'mpoun'ds with other polymerizable' compounds; for instance styrene or acrylonitrile:

The new penta-substitute'dthiophenol'plasticizers may also be ii1corporated directly "into '-the" original latex as obtained from the rubbentrecs or into the stabilizedlatex ready for shipment or into the latex of the rubber-like butadiene polymersobtainedby. emulsionlpolymerization, the. quantity of the new plasticizing agents being calculatedIon the rubber contentofthe latex:- After coagulating and working up the latexinthe usual manner the new plasticizing agent is present within the crude sheets in finely distributed form. The crude sheets are plasticized in the-*abovedeseribed manner: Of course, the new plasticizers are applied in a very finely dispersed form and derivatives are chosen; which, for instance, owing totheir wettability their specific gravity etc., provide a uniform and stable. suspensionrwithin the latex. Particularlyw suitable derivatives for application to latex are, for instance,,the.fiee. mercaptans, the diand trisulfi'ds the S acyliderivatives a-nd'the zinc salts. The new. plasticizingcagents-may also be employed in combina'tion with the" known wettingagents.

The :pentachloro-thiophenol may be prepared according to a known method by reacting. the hexachl-oro benzene'witli-alkalif metalsulfides or alkali metal hydrosulfid's-in-the presence of anhydrouslower aliphatic alcohols'attemperatu-res betWeen'llO and l30 C. Accordin'gto' the prior art process no quantitative yields are obtainedbwingto the formation offundesired by-products which are partially contained in the. thiophenols and which can be removedtheref'rom only by tedious purification methods. If thealcohol contains water, pen

taclilo'ro phenol is simultaneously formed by. hydrolysis whicli'can also be removedlwithdifficulty only.

According-to the. present invention pure penta-substitute'd' thiophenols adapted'for use as plasticizing agents are'obta'ir'ied in simple manner while'avoiding the above described diificulties by reacting. hexa-substituted ben-- zenefcoritainin-gat-least 5 chlorine atoms as substituents with alk'ali'metal disulfides-in the presence of an organic solvent'containing atleast one alcoholic hydroxy group.

ployedpth'e quantity of alcohol is to'be increased. in-

order' to attain-a quantitative reaction of the chlorinated benzene; derivatives the sodium" or potassium' disulfide has; tibe' applied in excess an'rounting to at least the 2.7 fold quantity of the'equimolar amount which-calculated on the hexa-substituted benzene-is required for the formation of the bis-penta-substituted plienyldisulfide.

As organic solvents containing at least one alcoholic hydroxyl group, the lower aliphatic and cycloaliphatic alcohols, such as mentha'nohethanol, propanol, butanol and cyclohexanol may advantageously be employed. The reaction may becarried outalsorin polyyalentalcohols; for instance, ethylene'glycol; butyleneglycolor monoethers thereof, for instance, ethylene glycol monomethyl' ether or butylene glycol monomethyl-eth'er:

In the reaction performed under the above described conditions only one chlorine atom of the hexa-substituted benzene is exchangedfor the-mercapto'group. The-alkali metal salts of the-thiophenols thus obtained are isolated from the solutions by removing-the solvent, for in'stance, by distilling off or by expelling with steam. For removin g impurities; if any, it' isadvisableto' takeup "the-"residue" with water wherein-thesodium salts of the thiophenols dissolve and to separate off the non-dissolved ingredients, for instance-,1 by; filtering; By. acidifying. the: aqueous solution=with mineralacidsrea g; HGlra'nd-SO'z: flier-free mercaptans are precipitated.

The pentachloro-thiophenol andthe tetrachloro-a'lkylthiophenols represent crystallized;- colorless: and: almost odorless" compounds being-1 insoluble? int wate'r,. slightly: sol-ublein ethylaleoh-ohand readily: soluble. in hot are-- Ina-tie hydroearbons anddn'r ligroim They are readily sol-uble'irr coldchloroform. The'lrcavy 'metal salts ofpentach'loro thiophenol i are' insoluble: in water: so: th'atl the mercaptans can' be purified or isolated hy-means i oftthesef salts:

Their alkali and: alkalineeearth metal salts of: the penta-substituted thiophenols; are 'soluble inwater. They! are readily; converted into'thein disulfidessbycmeans of oxidizing; agents; for instance, hydrogen. peroxide-,2 chlorine or potassium ferricyanide or by. means o'f air applied to the alkaline solution of said 1 thiophenols. The disulfidesrepresent weakly yellow" colored? crystallized compounds:

The aforesaidfunctional derivatives may: be produced' simple manner from the: pentaehloro thiophenol: on tetraehloro-alkylthiophenol. The zinc. saltsa'a're obtained by-rreaetion "of the sodium salts of: the pentaasub'stituted thiophenols in aqueous solution' with ammoniacal zincchloride solution; The acyl compounds may; be: prepared: in known -manner' by; reacting; the sodium salts 1 of the penta substituted thiophenols with the correspondingccar boxylic acid= chlorides in aqueous ororganic media. Acylation may;v also-be accomplished-by'means of 'c'ar boxylic anhydride preferably iir'therpresence"of organic tertiary bases. The thioa-cetals are obtainedfrom th'e: penta-substituted thiophenols and aldehydes on ketones in the presence ofraeid condensation agents; for: instance, hydrochloric acidor anhydrousxzinc chloride in indifferent organic solvents: The thiourethanes are'preferably: prepared byfusing; pentachloro thiophenol with: isocy-'- anstes: Thealkyl ethersimay; be obtained: according: to: the conventional I methods-= with? alkylating agentsg. for: in= stance, dialkylsulfates. Compounds containingcreactive halogen atoms, forinstance, cyanogen chloride; cyanogen bromide, chloro-acetonitrile, chloro-acetic acid,. chloro acetic ester, 2 chloro-benzotriazol; readilyv react: with penta-substituted thiophenols. The polysulfides are:- ob taiued by introduction of: sulfur; thus, for instance;.trisulfide-is formedzbyreacting 'penta-substitutednhiophenols and sulfur dichloride.

This application is a divisional application of our application-Serial-No. 207,068 of December 27,1950, now U. S. Patent-No. 2,695,898issued November 30;. 1954.

The following examples illustrate the 111'6561'1t1lflV811ti0fl' without restrictingv it thereto, the parts being by weighti Example] 950 parts of methanol, 225. parts of technical, water-containing. sodium sulfide and 44 parts oft sulfur are heated in a stirring-autoclave at 80 to 85 C. for 2 hours. The mixture is then cooled to 55 C., mixed with 284.4 parts of hexachloro-benzene and heated at 80 to 90 C. for further hours. The methanol is distilled off and the residue is takenu'p with Water. 1 The aqueous solution formed is suckedoff Whilestill warm, non-reacted portions of hexachloro-benzene, if any, being-re moved thereby. The mercaptan is quantitatively precipitated from the cold filtrate as slightly colored product in relatively pure-form by addition of an aqueous solution of S02 or .by introducing gaseous S02, care having to be taken that the pH-value is not smaller than 6. The preparation of a mercaptan being completely free from elementary sulfur is accomplished by desulfurizing the neutral-Washed crude material with a 10% aqueous sodium sulfite solution in water at 80 to"85 C. A technically pure pentachloro-thiophenol is thus obtained in a yield of 90 to 95% referred to hexachloro-benzene. The product melts between 228and 235 C. depending on the purity of the hexachloro-benzen'e employed.

In the same manner the corresponding, alkyl-substituted thiophenols are obtained from pentachloro-alky-lbenzenes for instance, pentachloro-tolucne and penta-' chloro-ethyl-benzene.

Example l 282 parts of technically pure pentachloro-thiophenol are dissolved with heating to to 80 C. in a solution of 41 parts of caustic soda in 2800 parts of water, the

solution remaining slightly turbid by: the di-pentachlorophenyl-disulfide formed by action of air. After cooling the solution to to C. a solution of 335 parts of potassium ferricyanide in 850 parts of water is dropped in with good stirring, the disulfide being quantitatively obtained thereby in light-yellow, very finely divided, almost pure form. After sucking off, Washing and drying the pure compound melting at 237 C. is obtained in form of coarse, orange crystals by crystallizing from chlorobenzene. p

In the above reaction potassium ferricyanide may be replaced by other oxidizingagents, such as hydrogen peroxide, air or sodium hypochlorite. v

Example 3 v 13 parts of sulfur dichloride at 40 to C..are slowly introduced into a solution of 70.5 parts of pentachlorothiophenol in 775 parts of carbon disulfide. The solution is stirred at to C. for some hours and the solvent is removed by distillation. After cooling the residue is ground with water and sucked off. After drying bispentachloro-phenyl trisulfide crystallizes from hot chlorobenzene in yellow crystals melting at 192.5 to 194.5 C.

Example 4 564 parts of technical pentachloro-phenol or a corresponding quantity of wet pentachloro-thioph'enol obtainedas described in Example ,1 aredissolvedin a solution of 90 parts of caustic soda in. 6000 parts of, water at to C. with the exclusion of. oxygen or air. Small non-dissolved portions are separated byj-sucking off. The clear, brown alkali salt solution of the mer-, captan is mixed with 'good stirring at room temperature with an ammoniacal zinc-chloride solution consisting, of 159.8 parts of crystallized zinc-chloride, 1500 parts of water and 827 parts of ammonia (161 parts of NH3 in 1000 parts of water). After 5 hours stirring the finely divided precipitated zinc salt of the pentachloro-thiophenol is sucked 011 and freed from salt by washing with 5% ammonia and water. 574 parts of odorless and colorless zinc salt of pentachloro-thiophenol decomposingat a temperature above 345 C. with discoloration without melting are obtained. The' yield calculated on pentachloro-thiophenol amounts to 96' to 97%.. i I.

Example, 5

:. hours stirring the precipitated benzoyl compound is sucked off, thoroughly washed with a sodium bicarbonateor sodium carbonate solution and water anddried. Thio-benzoic acid-S-pentachloro-phenyl ester melting at 137 to 139 C. is obtained as slightly colored,

odorless crystalline powder in comparatively pure form in ayield of 90 to calculated on pentachloro-thiophenol.

After complete purification by recrystallizing from acetone or benzene the product shows a melting point of 144.5 to C.

The S-acyl derivatives with aliphatic monoor dicarboxylic acids or other aromatic carboxylic acids, for instance, acetic acid, propionic acid, the fatty acids of the first runnings in the paralfin oxidation with a carbon chain of about Ca to C12, stearic acid or oxalic acid, maybe obtained in the same manner. When the reaction. is carried out in an anhydrous medium in the presence of tertiary bases the anhydrides of the aforesaid carboxylic acids may also be utilized.

Example 6 3 kilograms of smoked sheets are masticated with the addition of the following compounds in a Werner- Pfleiderer-mixer of the GK.6-type and the plasticity is determined by test samples drawn after certain periods indicated below.

plasticity number afterarnount. temperapercent ture, C. 0 6 8 10 V minminminminutes utes utes utes peutachlorothiophenol,

M. P. 239 C 0.2 130 510 190 165 1 2.4 trichlorothiopher101 (67% in hard paraffin) H 0.27 135 510 240 180 180 Example 7 1 kilogram of a butadiene copolymerizate obtained from 25 parts of styrene and 75 partsof butadiene is masticated on the roller at 120 C. With the addition of the following compounds and the plasticity is determined by test samples drawn after certain periods indicated below.

1 kilogram of a butadiene copolymcrizate obtained from 25 parts of acrylonitrile and 75 parts of butadiene are thermally plasticized in air with the addition of the 7 following compounds under an overpressure of 3 atmospheres andthe. plasticity is determined by test samples drawn after certain periodsindicated below.

the plasticity is determined by test samples drawn after plasticity number certain periods indicated below.

at r amount, temperapercent ture,

O. 0 30 60 plasticity number afterminminminutes utes utes amount, temperapercent ture,0. O 4 8 12 minminminminpentachloro-thiophenol,M. P. utes utes utes utes 230C 3.0 130 475 225 215 benzoic acid-pentachloro-thiophenylester, M. P. 131132 15 benzeneslllphonle a 0 3.0 130 475 245 245 pentachloro-thio- 1.2.4-tricl1l0rothlo-phenol (67% phenylester, M. P.

in hard paraifin) 4.0 130 475 240 275 193-197 0 0.5 120 545 280 180 ionnaldehyde-bls-pentachloro-phenyl-mercaptal, M. P. 270 0.. 0.5 120 545 185 140 100 benzaldehyde-bis-pentacbloro-phenyl-mercaptal, m. p. 108- 112 0 0.5 120 545 185 170 125 Example 9 40 kilograms of smoked sheets are masticated in a Example 12 45-liter Banbury mixer at 130 C. with 0.25% of the following compounds and at With 015% Of the l kilogram of smoked sheets is masticated on the roller followmg compounds for 7 mmutes and the plastlclty at 120 c. with the addition ot 0.50% of the following iS determined after thlS tlmfi. The crude sheet ShOWS compounds and the plasticity is determined by test ama plastlclty number of ples drawn after certain periods indicated below.

plasticity number aftert teluperaplastigity amoun ure, num er percent G, .after7 Omin- 6min- 10mm- 16mmminutes tes utes utes utes benzoie acid-pcntachloro-thiophenyl 0.25 130 340 ethyl-tetrac l -p y p e ester 0.15 150 205 M. P..107109O 505 180 130 100 zinc salt of the penta-chloro-thio- 0.25 130 205 11110 salt ofthe e y phenol 0.15 150 165 chloro-p eny e p 505 1 70 105 70 without addition. 130 380 N phenyl S penta chlorophenyl 0 150 365 thiourethane, M. P. 172.5174O. 505 95 65 hexamethylene di (S pentaehloroplienyl thlourethane), M.'P.'186.0- 1 1 1ss.0 0 505 130 100 di S pentachloro phenyl dis thio- V I carbonicester,M.P.227.5228.5 C... -505 40 45 di S peutachloro phenyl thio S oxallg eitler, 25l8g?C 505 100 60 55 -pen 8O oro-p eny O- Example 10 .nitrlle 505 205 V 145 125 3 kilograms of smoked sheets are masticated with the addition of the following compounds at the said temperaa0 tures in a Werner-Pficiderer-mixer of the GK.6-type and E a l the plasticity is determined by test samples drawn after, t .l certain periods indicated below. p 'f y Welght of a ground vulcamzate of a copolymerizate prepared from parts of butadtene and 55 25 parts of styrene containing about 40% of carbon black, are mixed as usual with 2 parts of pentachlorop ty number a-tte rr. thiophenol, 3 parts of fatty tar oil, 3 parts of brownnmount, tempera. coal tar-distillate and 3parts of an Edeleanu extraction percent -9 9 g product and treated in thereclaiming vessel with air utes utes utes utes 60 0f 3 atmospheres overpressure and steam of 4 atmospheres overpressure for minutes at atemperature of aceticucid-penta-chloroabout 150. 0. corresponding to the partial pressure of i fi the steam. -Highly plastic and viscous reclaimed rubber P. 117.5110 om. 0.2 123 035 280 220 155 henzpic acid-pentachlo with an averageplasticity number of 5 30 is thus obtained M 126 610 295 260 210 5 which-either alone or'in admixture with'unvulcanized 2.5 (li0li10r0h-1benzh0ic rubber, can be-made into vulcanizates with goodmei if chanical properties. 5 5 I 13 mm n n 0. 2 129 000 280 250 215 Reclalmed rubber with equal properties s obtalned by gl g g j 3 6 2 129 610 380 295 250 replacing the'pentachloro-thiophenol by 2 parts of the d meumel ioro-phenyi- 70 zinc salt of pentachloro-thiophenol. 50 kilograms of first trisulfidn, .1 I 9 9 0 Q2 545 425 370 245 quality ribbed smoked sheets are crushed'on the rollermill withcooling 'for 3 minutes and subsequently mastimethylestery p 5 cated within'30 minutes-The temperatures at the front 0 V 134 545 370 245 roll and the back roll as well as the temperature of the Y 76 elastorners and the plasticity' number according to Wi1- V 8 Example 11 l'kilogram of smoked sheets is masticated on the roller at C. with 0.5% of the following compounds and liams are determined within the intervals indicated in the following table:

[Plasticity number of the non-masticated rubber: 515] The acceleration of the mastication by addition of the Zinc salt of pentachloro-thiophenol at temperatures below 100 C. is evident from the above figures.

Example 15 Two portions of kilograms each of a copolymerizate of parts of butadiene and 35 parts of acrylonitrile are plasticized in a 45 liter Banbury kneader for 15 minutes or 30 minutes respectively. The following plasticity numbers (values) are determined according to Williams:

[Plasticity number of the non-treated rubber: 472.]

. 2.57 of penta- Plasticizing agent none chlorgthiophenol rubber rubber I Time of plasticizlng plasticity temperaplasticity temperanumber ture, number ture,

7 degrees degrees We claim:

1. A plasticized elastomer selected from the group consisting of natural rubber. rubbery conjugated diene polymers and their vulcanizates, containing as a plasticizer, a compound of the general formula Where R stands for a penta-substituted ph-enyl radical of the group consisting of CsClaand CsCla-alkr, alk. being an alkyl group containing from 1 to 8 C atoms, and X is selected from the group consisting of 2. A plasticized elastomer selected from the group consisting of natural rubber, rubbery conjugated diene polymers and their vulcanizates, containing as a plasticizer, acetylpentachloro-thiophenol.

3. A plasticized elastomer selected from the group consisting of natural rubber, rubbery conjugated diene polymers and their vulcanizates, containing as a plasticizer, benZoyl-pentachloro-thioph-enol.

References Cited in the file of this patent UNITED STATES PATENTS Williams Nov. 26, 1940 Starkweather Mar. 11, 1941 OTHER REFERENCES Noller: Chemistry of Organic Compounds, Saunders, 1951, pages 296, 297, 310-312. 

1. A PLASTICIZED ELASTOMER SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, RUBBERY CONJUGATED DIENE POLYMERS AND THEIR VULCANIZATES, CONTAINING AS A PLASTICIZER, A COMPOUND OF THE GENERAL FORMULA 